[EM] A DSV method inspired by SODA

[Jameson Quinn]

2011/7/30 <fsimmons at pcc.edu>

> One of the features of SODA is a step where the candidates decide what
> their approval cutoffs will be.on
> behalf of themselves and the voters for whom they are acting as proxies.
>  One of the many novel features
> is that instead of making these decisions simultaneously, the candidates
> make them sequentially with
> full knowledge of the decisions of the candidates preceding them in the
> sequence.
>
> I wonder if anybody has ever tried a DSV (designated strategy voting)
> method based on these ideas.
>
> Here's one way it could go:
>
> Voters submit range ballots.
>
> Factions are amalgamated via weighted averages, so that each candidate ends
> up with one faction that
> counts according to its total weight. For large electorates, these faction
> scores will almost surely yield
> complete rankings of the candidates.
>
> From this point on, only these rankings will be used.  The ratings were
> only needed for the purpose of
> amalgamating the factions.  If we had started with rankings, we could have
> converted them to ratings via
> the method of my recent post under the subject "Borda Done Right."  In
> either case, once we have the
> rankings from the amalgamated factions we proceed as follows:
>
> Based on these rankings the DSC (descending solid coalitions) winner D is
> found.  The D faction ranking
> determines the sequential order of play.  When it is candidate X's turn in
> the order of play, X's approval
> cutoff decision is made automatically as follows:
>
> For each of the possible cutoffs, the winner is determined recursively (by
> running through the rest of the
> DSV tentatively).  The cutoff that yields the best (i.e. highest ranked)
> candidate according to X's faction's
> ranking, is the cutoff that is applied to X's faction.
>
> After all of the cutoffs have been applied, the approval winner (based on
> those cutoffs) is elected.
>
> It would be too good to be true if this method turned out to be monotone.
>  For that to be true moving up
> one position in the sequence of play could not hurt the winner.  Although I
> think that this is probably
> usually true, I don't think that it is always true.  Anybody know any
> different?
>


I'm pretty certain that even if a method like this could be monotone, the
amalgamation in the first step breaks it, because of a "candidate hijacking"
strategy.

I have no opinion if some other way to do this step would give monotonicity.
I'd like to think so, but I wouldn't bet on it.

JQ

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